Cancer of the prostate is a serious health problem both in the US and worldwide. In the US alone approximately 165,000 new cases of prostate cancer are diagnosed each year (Cancer Statistics 12993, CA Cancer J. Clin. 43:7-26, 1993), new types of treatments such as immunotherapy should be considered. The purpose of the present study is to explore the possibility of inducing cytotoxic T lymphocyte (CTL) responses to prostate-related antigens as a means of developing antigen-specific immunotherapies for prostate cancer. Potential CTL antigenic epitopes have been identified from the sequences of PSA and PAP. The identification of these potential CTL epitopes was achieved by selecting sequences from PSA and PAP that contain anchor binding motifs for MHC class I molecules. Several of these peptides bind with high affinity to purified MHC molecules. The ultimate goal of the Phase I study is to identify the immunogenic HLA-A2.1-restricted peptides from PSA and PAP that are capable of eliciting CTL that will kill cells expressing these prostate-related proteins. If funded, the Phase II studies will be targeted to develop this peptide(s) into a CTL-inducing immunotherapeutic for treatment of advanced prostate cancer.